add FieldDoesNotExist exception to __all__
add FieldDoesNotExist exception to __all__

So it will be available when you do:
    from mongoengine import *

touilleMan/mongoengine,MakerReduxCorp/mongoengine,Davidrjx/mongoengine,blaggacao/mongoengine,WingGao/mongoengine,9nix00/mongoengine,eli-b/mongoengine,muhammad-ammar/mongoengine,nicolascine/mongoengine,ms5/mongoengine,cogniteev/mongoengine,prijindal/mongoengine,khallaghi/mongoengine,MongoEngine/mongoengine,elephanter/mongoengine,gmacon/mongoengine,jimmyshen/mongoengine,Davidrjx/mongoengine,gavincabbage/mongoengine,iandd0824/mongoengine,starsirius/mongoengine,larsbutler/mongoengine,noirbizarre/mongoengine,DavidBord/mongoengine,ConsumerPhysics/mongoengine,Catstyle/mongoengine,cogniteev/mongoengine,nathanial/mongoengine,MRigal/mongoengine,reallistic/mongoengine,RussellLuo/mongoengine,losintikfos/mongoengine,sourcelair/mongoengine,ProgressivePlanning/mongoengine,yarneo/mongoengine,MakerReduxCorp/mongoengine